Welding, or fusion welding, of thermoplastic polymer composites is a well-known process for joining composites. Fusion welding is accomplished wherein portions of the polymers to be joined are partially melted (or softened) to allow the polymer chains at the interface to diffuse into one another. The interdiffusion occurs in a large length scale, allowing chain entanglement to form at the interface. Essentially, two separated polymers become one. This polymer joining method is non-reversible, as it relies on the polymer chains at the interface to fuse into each other and form one phase.